Cathode-ray tube



Dec. 25, 1951 J. s. LOCKYER CATHODE-RAY TUBES Filed July 6, 1950 13 \NVENTOR Y R.T T K A Cw 0 M 8. JW

Patented Dec. 25, 1951 CATHODE-RAY TUBE John Shapland Lockyer, London, England, as-

signor to Ferguson Radio Corporation Limited, London, England, a company of Great Britain Application July 6, 1950, Serial No. 172,322 In Great Britain July 6, 1949 4 Claims.

1 In cathode ray tube apparatus using magnetic focusing of the cathode ray on the luminescent screen of the tube, it is often desirable, and in cathode ray television receivers usually essential,

to provide means whereby the image formed by the ray may be centralised on the screen, since no perfectly symmetrical tube, deflector assembly or focusing magnet can be produced commercially.

The invention relates to a method of producing deflections of the image without any major eifects on the picture size, shape, or focus, by the introduction of a flat ring of magnetic material, held reasonably close to the focusing assembly in such a manner that it can be moved in a radial direction. The deflection imparted to the picture is approximately at 90 to that given to the magnetic ring.

An object of this invention is to provide apparatus whereby the ring of magnetic material can be moved in a radial direction by means of a single operators control.

Another object is to provide such apparatus which also has the advantage of simple construction.

According to this invention, cathode ray tube apparatus, including a magnetic focusing assembly and a ring of magnetic material disposed substantially co-axially with and close to the focusing assembly and movable radially with respect to the axis of this assembly, is provided with mounting means for the ring of magnetic material including a lead screw-and-nut device operable for displacing the ring along a line perpendicular to the said axis, a pivot having an axis i parallel to the axis of the assembly and substantially perpendicular to the said line, and a common control member rotatable to operate the lead screw-and-nut device and operable as a lever to displace the ring about the pivot.

In a preferred arrangement the ring of magnetic material is slidable on an intermediate member which is carried by a pivot fixed in relation to the focusing assembly. The control member in this case may be a nut or screw engaged with a screw or an internally screwed hole on or in the ring of magnetic material, the control nut or screw co-operating with a thrust bearing on the intermediate member.

An embodiment of the invention, suitable for use in a domestic television receiver, will be described with reference to the accompanying drawings in which:

Fig. 1 is a side elevation of the image centralising means Fig. 2 is a view of the same means obliquely from the front,

Fig. 3 is a side elevation to a smaller scale of a part of acathode ray tube apparatus provided with the means shown in Figs. 1 and 2.

As shown in Fig. 3, the cathode ray tube I9 is provided with an annular magnetic focusing assembly surrounding the neck of the tube behind the flare and fixed in position in relation to the tube in the usual manner. The focusing assembly includes a front ring l2 having a plane front face. A lug l3 extending downwards from the front ring i2 carries a pivot screw l4 disposed parallel to the assembly axis and fixed to the lug I3 by nuts. An intermediate supporting member l5 pressed from sheet non-magnetic metal has an aperture rather larger in diameter than the neck of the cathode ray tube. A shallow rectangular channel opening forwards is formed vertically in the middle of the supporting member IS. The base of this channel at the bottom of the supporting member I5 is apertured to take the pivot screw l4, and the channel accommodates a head on the pivot screw. At the back and the top of the supporting member is a resilient finger l3 pressing on the back of the front ring |2 of the focusing assembly and held by nuts on a screw |9 passin through the base of the channel IT. The finger 18 provides a clamping arrangement to prevent accidental movement of the supporting member. At the top end of the channel is a forwardly projecting eye lug 29 the axis of the eye which is vertical.

The ring 2| of magnetic material is flat and lies against the front of the supporting member 5. The ring 2| is slidably guided for vertical movement by flanges 22 struck forward at the sides of the supporting member and co-operating with vertical flats 23 formed at the sides of the ring 2i. Parts of the flanges 22 are struck inwards over the face of the ring 2| in order to keep this ring against the supporting member. A vertical lead screw 24 has its lower end fixed to the ring 2| near its top and passes through the eye lug 2|] above which it is engaged in a tubular nut 25 forming the control member. A helical spring 26 surrounds the screw 2 and is compressed between the eye lug 2!} and the ring 2|.

Rotation of the tubular nut 25 about its own axis raises and lowers the ring 2| of magnetic material relatively to the focusing assembly ll. Transverse displacement of the nut 25 acting as a lever causes the supporting member 5 and the ring 2| to rock about the pivot screw l4. so that the centre of the ring moves in an arcuate path substantially perpendicular to the axis of the lead screw 24.

The device therefore enables one control member to be used for imparting static deflections to the picture in the vertical or the horizontal direction as required.

I claim:

1. Cathode ray tube apparatus including a cathode ray tube, a magnetic focusing assembly surrounding said tube, a ring of magnetic material disposed substantially co-axially with and close to said focusing assembly, and means supporting said ring from said focusing assembly, said supporting means including a lead-screwand-nut device operable for displacing said ring along a line substantially perpendicular tothe axis of said assembly, a pivot having an axis parallel to the axis of said assembly and substantially perpendicular to said line and a common control member rotatable to operate the lead screw-and-nutdevice and operable as a lever to displace said ring about said pivot.

2. Cathode ray tube apparatus including a cathode ray tube, a magnetic focusing assembly surrounding said tube, a ring of magnetic material disposed substantially co-axially with and close to said focusing assembly, and means supporting said ring from said focusing assembly, said supporting means including an intermediate member, a pivot having an axis parallel to the axis of said assembly and connecting said intermediate member to said assembly, said intermediate member forming a slide supporting'said ring, a lead screw-and-nut device .co-operating with said ring and said intermediate member for displacing said ring along a line perpendicular to the axis of said pivot, said lead screw-and-nut device comprising a rotatable control member which is operable also as a lever to displace said ring together with said intermediate member about said pivot.

3. Apparatus as claimed in claim ;2, wherein the control member is a nut engaged with a screw. on said ring, the intermediate member comprising a thrust bearing co-operating with said nut.

4. Apparatus as claimed in claim 2, and including frictional means co-operating with said intermediate member and said assembly for the purpose of restraining their relative displace ment about said pivot.

JOHN SHAPLAND LOCKYER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS.

Quam Dec. 12, 1950 

